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  • Flatulence, or passing gas, is a normal daily phenomenon.

  • Most individuals, yes, that includes you, will make anywhere from 500-1500 milliliters of gas,

  • and can pass gas ten to twenty times a day.

  • But where does this bodily gas come from?

  • A small proportion may come from ingesting air during sleep, or at other times,

  • but the majority of gas is produced by bacteria in our intestines as they digest parts of food which we cannot.

  • Our intestine is home to trillions of bacteria living in a symbiotic relationship with us.

  • We provide them with a safe place to stay and food to eat.

  • In exchange, they help us extract energy from our food,

  • make vitamins for us, like vitamin B and K, boost our immune system,

  • and play an important role in gastrointestinal barrier function, motility and the development of various organ systems.

  • Clearly, it's in our best interest to keep these bacteria happy.

  • Gut bacteria get their nutrition primarily from undigested food,

  • such as carbohydrates and proteins, which come to the large intestines.

  • They ferment this undigested food to produce a wide range of compounds,

  • such as short-chain fatty acids and, of course, gases.

  • Hydrogen and carbon dioxide are the most common gaseous products of bacterial fermentation, and are odorless.

  • Some people also produce methane due to specific microbes present in their gut,

  • but methane is actually odorless, too.

  • Well then, what stinks?

  • The foul smell is usually due to volatile sulfur compounds,

  • such as hydrogen sulfide and methanethiol, or methyl mercaptan.

  • These gases, however, constitute less than 1 % of volume,

  • and are often seen with ingestion of amino acids containing sulfur,

  • which may explain the foul smell of gas from certain high protein diets.

  • Increased passage of gas is commonly noticed after eating foods with high amounts of indigestible carbohydrates,

  • like beans, lentils, dairy products, onions, garlic, leeks, radishes,

  • potatoes, oats, wheat, cauliflower, broccoli, cabbage, and brussel sprouts.

  • Humans lack the enzymes,

  • so the bacteria able to ferment complex carbohydrates take over,

  • and this naturally leads to more gas than usual.

  • But if you feel uncomfortable, bloated or visibly distended,

  • this mean indicate impaired movement of gas along the gastrointestinal track.

  • It's important not to just blame certain foods for gas and bloating and then avoid them.

  • You don't want to starve the bacteria that digest these complex carbohydrates,

  • or they'll have to start eating the sugars in the mucus lining of your intestines.

  • Your personal gas will vary based on what you eat, and what bacteria are in your gut.

  • For example, from the same starting sugar,

  • the bacteria clostridium produces carbon dioxide, butyrate and hydrogen,

  • while propionibacterium can produce carbon dioxide, propionate and acetate.

  • At the same time, methanogens can use hydrogen and carbon dioxide produced by other bacteria to generate methane,

  • which can reduce the total volume of gas by using up hydrogen and carbon dioxide.

  • So there's a complex web among intestinal bacteria

  • allowing them to flourish by either directly consuming undigested food, or using what other bacteria produce.

  • This interaction largely determines the amount and type of gas produced,

  • so gas production is a sign that your gut bacteria are at work.

  • But in some instances, people may develop abnormal increased flatulence.

  • A common example is lactose intolerance.

  • Most individuals have the enzyme for breaking down lactose, a sugar present in milk and milk-derived products.

  • But some people either lack it entirely, or have a reduced amount,

  • such as after a gastrointestinal infection,

  • so they're unable to digest lactose products and may experience cramping,

  • along with increased flatulence due to bacterial fermentation.

  • But remember, most gas is produced as a natural result of bacterial in the intestine,

  • and indicates healthy functioning of the gut.

  • The amount and type can based on your diet and the bacteria in your intestine.

  • Exercise social courtesy while passing gas, and do try to forgive your bacteria.

  • They're only trying to be helpful.

Flatulence, or passing gas, is a normal daily phenomenon.

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B2 US TED-Ed bacteria gas gut carbon dioxide dioxide

【TED-Ed】Why do we pass gas? - Purna Kashyap

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    朱朱 posted on 2014/09/24
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